Seismic surveying is used for identifying subterranean geological structures, such as hydrocarbon layers, fresh water aquifers, and so forth. In performing seismic surveying, seismic sources are placed at various locations on an earth surface or sea floor (or in a wellbore), with the seismic sources activated to generate seismic waves directed into a subterranean structure. Examples of seismic sources include explosives, air guns, or other sources that generate seismic (acoustic) waves. In a marine environment, seismic sources and sensors can be towed in water by a sea vessel.
The seismic waves generated by a seismic source travel into the subterranean structure, with a portion of the seismic waves reflected back to the surface (earth surface, sea floor, or wellbore surface) where they may be detected by seismic sensors (e.g., geophones). These seismic sensors produce signals that represent detected seismic waves. Signals from the seismic sensors are processed to yield information about the content and characteristic of the subterranean structure.
Time-lapse seismic surveying involves the use of two or more seismic surveys acquired at different times to measure production-related or other development effects on a subterranean structure, such as a reservoir production. Conventional techniques for time-lapse seismics typically monitor fluid and other property changes which may occur during development (e.g., fluid extraction) of the subterranean structure. However, time-lapse seismic surveying does not provide a complete picture of changes that may occur in the subterranean structure due to development. Therefore, a model of the subterranean structure based on conventional time-lapse seismic surveying techniques may not be accurate or complete.